Study: High seafood diet may increase risk of exposure to 'forever chemicals'

April 12 (UPI) -- A new U.S. study into so-called "forever chemicals" in seafood published Friday recommends the introduction of stricter public health guidelines for the amount of marine fish and shellfish people can safely consume.

The Dartmouth College research into the seafood consumed by 1,829 New Hampshire "Granite Slaters" found those who ate the most may face a higher risk of exposure to perfluoroalkyl and polyfluoroalkyl substances, or PFAS, manmade chemicals that in humans are linked to cancer, fetal abnormalities, high cholesterol, and thyroid, liver, and reproductive disorders, the study's authors said in a news release.

Cross-referencing an analysis of PFAS concentrations in fresh seafood against a statewide survey of eating habits the research, published in the journal Exposure and Health, set out to close an understanding gap of the risk-benefit of consuming seafood to help people make informed diet decisions, in particular vulnerable groups including children and expectant mothers.

The study also drew on extensive data gathered by the state on other sources of PFAS, from drinking water to plastics and non-stick coatings to fire-fighting foams and many more, a legacy of the versatility the molecular stability of these toxins bring -- but which also makes them virtually indestructible, hence the forever chemicals moniker.

"Most existing research focuses on PFAS levels in freshwater species, which are not what people primarily eat. We saw that as a knowledge gap in the literature, especially for a New England state where we know people love their seafood," said Geisel Medical School Epidemiology Associate Professor and study co-author Megan Romano.

Tests for 26 PFAS types in samples of the most popular species including cod, haddock, lobster, salmon, scallop, shrimp, and tuna purchased fresh from a market on the coast of the state found the highest concentrations in shrimp and lobster averaging as high as 1.74 and 3.30 nanograms per gram, but the other species had overall readings of less than 1 nanogram per gram.

The study cautioned that the ubiquity of PFAS in the environment made it difficult to know exactly where and how the chemicals enter the marine food chain, but warned that shellfish may be particularly susceptible to the accumulation of PFAS in their cells due to feeding and living on the seafloor, as well as their proximity to sources of PFAS entering the sea from land.

In addition, larger marine species may ingest PFAS by eating smaller species with PFAS deposits.

The team's eating survey found high daily seafood consumption levels among New Hampshire men and women at around an ounce, exceeding the levels reported by the National Health and Nutrition Examination Survey for the northeast, and more than 1.5 times the national average for both. At 0.2 ounces daily, consumption by New Hampshire children aged 2 to 11 years old was at the top end of the range for children nationwide.

Nearly all adults reported consuming seafood within the past year of whom 94% ate fish or shellfish within the previous month and two-thirds had eaten seafood within the past week but the data revealed significant differences according to where respondents lived and their socio-economic status.

Among people whose annual household income was sub-$45,000 per year, more than 60% reported consuming seafood at least once per week, compared with higher income household incomes who ate seafood less frequently.

Romano said the study's recommendation was not to avoid seafood given its proven value as a source of lean protein and omega fatty acids, but to draw attention to a potentially underestimated source of PFAS exposure in humans.

The authors stressed that the need for more stringent safety guidelines is especially urgent for coastal regions such as New England where a legacy of industry pollution and PFAS contamination creates a reality where fish is integral to the culture.

"PFAS are not limited to manufacturing, fire-fighting foams, or municipal waste stream -- they are a decades-long global challenge," said study co-author Jonathan Petali, a toxicologist with the New Hampshire Department of Environmental Services.

"New Hampshire was among the first states to identify PFAS in drinking water. We're a data-rich state due to years spent investigating the impacts of PFAS and trying to mitigate exposure."

Middlebury College Environmental Studies assistant professor and co-author Kathryn Crawford said establishing safety guidelines would help protect people who are especially susceptible to pollutants but said people with more typical consumption habits need not worry.

"Seafood consumption advisories often provide advice for those individuals that is more conservative than for the rest of the population. People who eat a balanced diet with more typical, moderate amounts of seafood should be able to enjoy the health benefits of seafood without excessive risk of PFAS exposure," she said.

Mercury and other contaminants are covered by federal guidelines but none exist for PFAS, said Celi Chen, co-author of the study and a research professor at Dartmouth's Biological Sciences Department.

"Top predator species such as tuna and sharks are known to contain high concentrations of mercury, so we can use that knowledge to limit exposure. But it's less clear for PFAS, especially if you start looking at how the different compounds behave in the environment."

The research was funded with the help of grants from the National Institute of Environmental Health Sciences and the National Institute of General Medical Sciences.